Bonding resin for wood-based composites providing light coloring, low platen sticking, and water resistance

ABSTRACT

Disclosed herein are adhesives, wood-based composites incorporating the adhesives, and methods of forming wood-based composites using the adhesives. Wood-based composites formed using the adhesives demonstrate an optimal combination of characteristics desirable to the wood products industry. Specifically, the wood products formed using the adhesive demonstrate (1) a light appearance when wet; (2) relatively low moisture content after soaking in water; (3) relatively little thickness swelling after soaking in water; and (4) minimal adhesion to metal press platens during press-forming of the wood products.

CROSS REFERENCE AND RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 14/338,606, filed Jul. 23, 2014, which is incorporated hereinby reference in its entirety. To the extent the foregoing applicationand/or any other materials incorporated herein by reference conflictwith the present disclosure, the present disclosure controls.

BACKGROUND

Wood-based composites are widely used in North America in bothstructural and non-structural applications. Structural applicationsinclude use of these materials for framing and sheathing (floors, wallsand roofs) in residential construction. One of the most commoncomposites used for these applications is oriented strandboard (OSB).

OSB is typically manufactured in seven major stages, which includestranding, screening, drying, blending, forming, pressing, andfinishing. Stranding is a process in which logs are cut into discretewooden strands (also known as flakes) that typically have an aspectratio between 1 and 20. The long axis of the strands is predominantlyaligned within about 0-30° of the grain of the wood. The strandthickness can range from about 0.015″ to about 0.050″ and the length canrange from about 1″ to about 12″, or even longer. In most cases, it isadvantageous to cut strands from wood that has a relatively highmoisture content, such as 30-200%. Thus, the stranding process almostalways yields wet strands that must be dried prior to furtherprocessing. Drying is usually accomplished by passing the wet strandsthrough long rotating drums or pipes in conjunction with hot, dry air.Alternatively, strands can be dried by conveying them in a chamber withhot, dry air passing through or around the conveyance system. The dryingprocess commonly results in strands that have a moisture content ofabout 1-7%. The resulting dried strands exist as a mixture of relativelylarge and small elements, and it is frequently desirable to screen thematerial in order to separate the strands on the basis of size. In manycases the smallest wooden particles, known as fines, are diverted fromthe product stream and are transported to a burner where they are usedas fuel. The acceptable wooden strands are then metered into largerotating drums, known as blenders, and are sprayed or otherwise mixedwith bonding resin (adhesive) and wax. This stage is known as blending.Many blenders rotate at a rate of about 4-20 rpm and are tilted (3-8°)in order to promote material flow. A single blender can have about sixliquid application devices distributed within it. Such applicationdevices are frequently rotary disk atomizers, but they can also besimple spray guns. In some cases one of the application devices isdevoted to wax and five of the application devices are devoted to resin.Powdered bonding resins can also be introduced into the blender. It iscommon for large strands and small strands to be blended separately.Strands that have been treated with bonding resin and wax are thenformed into a mat. Treated strands are formed into a mat by dispensingthem at some controlled rate through mechanical partitions that tend toalign the strands in a particular orientation. As the strands passthrough the alignment devices they are collected onto a continuousconveyor belt. Frequently, the strands incorporated into the top andbottom layers of an OSB mat are larger than the strands incorporatedinto the core (or middle) layer of the mat. In many cases the bondingresins and application levels used in the surface layers of an OSB matare different than those used in the core layer of the mat. In acommercial manufacturing process the mat is generally continuous inlength and has a width of between about 4′ and 16′. The thickness of themat can be in the range of about 2″ to 20″. In some cases the continuousmat of treated strands is transported directly into a continuoushot-press, but in most cases the mat is cut into discrete sections,which commonly have a length of about 8′ to 20′. These mat sections areloaded into a multi-opening hot press, which can usually press between12 and 20 mats simultaneously. During the process of pressing strandsare forced together and intimate contact is achieved along theirinterface. Subsequent to this consolidation process bond formationoccurs as the resin undergoes curing reactions and is converted from aliquid to a load-bearing solid. The press then opens and the relativelylarge “jumbo” panels are ejected onto a conveyor and transported to thefinishing stages of the operation. Finishing steps commonly includecutting the jumbo panels into smaller panels, such as those havingdimensions of 4″×8″. Other finishing activities can include sanding,edge profiling, marking with grade stamps, grading for quality, stackinginto units, sealing, labeling, strapping and packaging.

It is common for OSB panels to be manufactured by use of PMDI (polymericmethylene diphenyldiisocyanate) as a core-layer adhesive and PF(phenol/formaldehyde) resin as a surface layer adhesive. The PMDI isrelatively expensive and it bonds to metal press platens. Thus, PMDI isnot usually used as a surface layer adhesive, but it is associated withsignificantly improved water absorption rate when the resulting OSB isexposed to precipitation during the construction process. The PMDI hasthe further advantage of resulting in increased bond strength betweenadjacent strands, as compared to PF adhesive. Thus, many OSBmanufacturers use PMDI as the adhesive in the core layer as opposed toPF resin.

In order to achieve even lower water absorption rate, a few OSBmanufacturers have replaced PF adhesive in the surface layer of thepanel with PMDI. This results in an OSB panel with exceptional waterresistance. A further benefit to this practice is that the panel retainsa relatively light-color when it is exposed to water, as opposed to adark, brown color which is commonly experienced by OSB that is made witha PF adhesive in the surface layer and is subsequently exposed to water.Unfortunately, OSB manufacturers who utilize PMDI in the surface layermust exert significant effort to ensure that the PMDI-treated woodenstrands do not bond to the steel platens in the hot-press. Typically,prevention of press sticking is achieved by application of releaseagents to the top and bottom of the strand mat just prior tohot-pressing. Unfortunately, the release agents (usually tall oil fattyacid soaps or wax emulsions) are relatively expensive and they tend todarken the surface of the OSB, which lessens the value of the panel inthe marketplace. The release agents can also accumulate on the pressplatens and some of them promote corrosion of the press platens. Thus,most OSB manufacturers choose not to use PMDI in the surface layer ofthe OSB, although it would be beneficial to panel properties.

Thus, there is a need for an alternative surface layer adhesive for OSBand other wood-based composites that achieves a light-colored surface,reduced water absorption rate, and is associated with less sticking tothe steel press platens during the manufacturing process.

SUMMARY

This summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This summary is not intended to identify key features ofthe claimed subject matter, nor is it intended to be used as an aid indetermining the scope of the claimed subject matter.

Disclosed herein are adhesives, wood-based composites incorporating theadhesives, and methods of forming wood-based composites using theadhesives. Wood-based composites formed using the adhesives demonstratean optimal combination of characteristics desirable to the wood-productsindustry. Specifically, the wood products formed using the adhesivedemonstrate (1) a light appearance when wet; (2) relatively low moisturecontent after soaking in water; (3) relatively little thickness swellingafter soaking in water; and (4) minimal adhesion to metal press platensduring press-forming of the wood products.

While known adhesives may provide superior performance for certain ofthese characteristics, no known adhesives provide the optimalcombination of the disclosed embodiments. As one example, polymericmethylene diphenyldiisocyanate (PMDI) adhesive provides orientedstrandboard (OSB) with less thickness swelling after a water-soak testthan OSB formed with the disclosed adhesives, but the PMDI OSB is alsofar inferior with regard to adhesion to press platens, which affectsmanufacturing efficiency. Accordingly, the disclosed adhesives,wood-based composites, and methods of forming wood-based compositesprovide overall superiority in characteristics vital to themanufacturing of wood-based composites, when compared to the presentstate of the art.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description, whentaken in conjunction with the accompanying FIGURE, which illustratesexperimental results related to the lap shear strength of adhesivebonding between wood and metal for a variety of adhesives, includingadhesives according to the disclosed embodiments.

DETAILED DESCRIPTION

Disclosed herein are adhesives, wood-based composites incorporating theadhesives, and methods of forming wood-based composites using theadhesives. Wood-based composites (also referred to herein as “woodproducts”) formed using the adhesives demonstrate an optimal combinationof characteristics desirable to the wood products industry.Specifically, the wood products formed using the adhesive demonstrate(1) a light appearance when wet; (2) relatively low moisture contentafter soaking in water; (3) relatively little thickness swelling aftersoaking in water; and (4) minimal adhesion to metal press platens duringpress-forming of the wood products.

While known adhesives may provide superior performance for certain ofthese characteristics, no known adhesives provide the optimalcombination of the disclosed embodiments. As one example, PMDI providesoriented strandboard (OSB) with less thickness swelling after awater-soak test than the disclosed embodiments (see, Table 7), but alsois far inferior with regard to adhesion to press platens (see, FIGURE).While OSB is used as an exemplary wood-based composite throughout thisdisclosure, it will be appreciated that adhesives of the type disclosedcan be used to form any wood-based composite known to those of skill inthe art.

Adhesive Emulsions

In one aspect, an adhesive emulsion is provided. In one embodiment, theadhesive emulsion includes:

-   -   (a) a continuous phase, comprising an aqueous, alkaline solution        comprising a melamine/urea/formaldehyde resin; and    -   (b) a dispersed phase, comprising a multifunctional aromatic        isocyanate component;    -   wherein the aqueous, alkaline solution comprising the        melamine/urea/formaldehyde resin has a percent solids content of        about 1.0% to about 90.0%, and wherein the        melamine/urea/formaldehyde resin and the multifunctional        aromatic isocyanate component are present in a ratio of about        92:8 to about 40:60 on a solids mass basis. As used herein, the        term “about” indicates that a defined value can be modified by        greater than or less than 5%.

The adhesive emulsion comprises a continuous phase and a dispersedphase. The continuous phase comprises at least an aqueous, alkalinesolution. The aqueous, alkaline solution comprises amelamine/urea/formaldehyde (“MUF”) resin. In one embodiment, themelamine/urea/formaldehyde resin is a condensation polymer derived frommelamine, urea, and formaldehyde.

The properties of wood products formed using the adhesive emulsion canbe modified based on the relative amounts of each component of the MUFresin.

Any composition of the MUF resin can be used in the disclosedembodiments. With regard to melamine, in one embodiment themelamine/urea/formaldehyde resin comprises a melamine-based componentthat is 5.0% or greater of the solids mass of the MUF resin. In oneembodiment the melamine/urea/formaldehyde resin comprises amelamine-based component that is 2.0% to 50.0% of the solids mass. Inone embodiment the melamine/urea/formaldehyde resin comprises amelamine-based component that is 5.0% to 30.0% of the solids mass. Inone embodiment the melamine/urea/formaldehyde resin comprises amelamine-based component that is 7.0% to 20.0% of the solids mass.

With regard to urea, in one embodiment the melamine/urea/formaldehyderesin comprises a urea-based component that is 5.0% or greater of thesolids mass of the MUF resin. In one embodiment themelamine/urea/formaldehyde resin comprises a urea-based component thatis 10.0% to 80% of the solids mass. In one embodiment themelamine/urea/formaldehyde resin comprises a urea-based component thatis 20.0% to 70.0% of the solids mass. In one embodiment themelamine/urea/formaldehyde resin comprises a urea-based component thatis 30.0% to 60.0% of the solids mass.

With regard to formaldehyde, in one embodiment themelamine/urea/formaldehyde resin comprises a formaldehyde-basedcomponent that is 30.0% or greater of the solids mass of the MUF resin.In one embodiment the melamine/urea/formaldehyde resin comprises aformaldehyde-based component that is 10.0% to 50.0% of the solids mass.In one embodiment the melamine/urea/formaldehyde resin comprises aformaldehyde-based component that is 15% to 45% of the solids mass. Inone embodiment the melamine/urea/formaldehyde resin comprises aformaldehyde-based component that is 20.0% to 40.0% of the solids mass.

In certain embodiments, the aqueous, alkaline solution comprising amelamine/urea/formaldehyde resin has a pH of about 7.5-11. In oneembodiment, the aqueous, alkaline solution comprising amelamine/urea/formaldehyde resin has a pH of about 8.0-10.0. In oneembodiment, the aqueous, alkaline solution comprising amelamine/urea/formaldehyde resin has a pH of about 8.5-9.5.

In order to achieve the desired pH value for the aqueous, alkalinesolution comprising a melamine/urea/formaldehyde resin, in oneembodiment the aqueous, alkaline solution comprising themelamine/urea/formaldehyde resin further comprises an alkalinecomponent. Alkaline components suitable for use in the disclosedembodiments include sodium hydroxide, potassium hydroxide, ammoniumhydroxide, or organic amines, such as triethanolamine.

The MUF resin can be incorporated into the aqueous, alkaline solution atany amount that allows for the adhesive emulsion to form (i.e., exist asan emulsion). The MUF resin is solvated (i.e., dissolved) in theaqueous, alkaline solution. In one embodiment, the aqueous, alkalinesolution comprising the melamine/urea/formaldehyde resin has a percentsolids content of about 1.0% to 90.0%. In one embodiment, the aqueous,alkaline solution comprising the melamine/urea/formaldehyde resin has apercent solids content of about 40.0% to 70.0%.

Representative commercial examples of the aqueous, alkaline solutioncomprising a melamine/urea/formaldehyde resin include Casco Resin MUFM08PC-T and M20PC-T (Momentive Specialty Chemicals, Louisville, Ky.),and 401 W67 (Georgia-Pacific Chemicals, LLC, Atlanta, Ga.).

The adhesive emulsion may further include an additive selected from thegroup consisting of surfactants, diluents, viscosifying agents,colorants, preservatives, formaldehyde scavengers, and combinationsthereof. Such additives would comprise a minority of the emulsion andmay be contained within the continuous phase or the dispersed phase.These additives can be used to improve the performance or processingcharacteristics of the adhesive emulsion or wood product formedtherefrom.

One unique aspect of the adhesive emulsion is that the continuous phaseand the dispersed phase can be selected in such a way that no catalystis needed to facilitate the reaction between the phases to solidify theadhesive. Accordingly, in one embodiment, the adhesive emulsion containsno catalyst.

The dispersed phase comprises a multifunctional aromatic isocyanatecomponent that is reactive with the MUF resin of the continuous phase.In one embodiment, the multifunctional aromatic isocyanate componentcomprises PMDI (polymeric methylene diphenyldiisocyanate, which istypically a mixture of MDI and MDI oligomers, and1,5′-naphthalenediisocyanate); toluene 2,4-diisocyanate, toluene2,6-diisocyanate, mixtures of toluene 2,4-diisocyanate and toluene2,6-diisocyanate (TDI), 2,4′-methylene bis(phenylisocyanate),4,4′-methylene bis(phenylisocyanate) (MDI), and combinations thereof.Manufacturers of multifunctional aromatic isocyanates include BASFCorporation (Wyandotte, Mich.), Huntsman Corporation (The Woodlands,Tex.), The Dow Chemical Company (Midland, Mich.), and Bayer Corporation(Pittsburgh, Pa.).

The dispersed phase may include components besides the multifunctionalaromatic isocyanate component. However, in one embodiment the dispersedphase consists essentially of the multifunctional aromatic isocyanatecomponent.

In one embodiment the ratio of the MUF resin to the multifunctionalaromatic isocyanate is about 92:8 to 40:60 on a solids mass basis. Asthe MUF resin portion increases, a wood-based composite formed from theadhesive emulsion becomes less likely to stick to metal press platens.Relatively higher MUF resin also creates wood-based composites with ahigher water absorption rate. As the isocyanate level increases, awood-based composite formed from the adhesive emulsion becomes morelikely to stick to metal press platens and wood-based composites formedfrom the adhesive emulsion have a lower water absorption rate.

The relative proportions of the two components also affect the pot lifeof the resin. The closer the MUF emulsion to isocyanate mass ratio getsto 1:1, the faster the adhesive cures.

The “solids mass” of an MUF resin is determined by loading a smallweighing pan with about 1-3 g of wet resin sample and measuring thisloaded mass to about four decimal places. The loaded pan (usuallyreplicated) is transferred into an oven that is maintained at atemperature of about 125° C. for a period of about 3.5 hours. The loadedpans are then removed from the oven and weighed on an analytical balancein order to determine the mass of resin residue. The percent “solidsmass” of the resin is then calculated by the following equation:

Percent Solids Mass of Resin=(100%)(wet resin mass−dry resin mass)/(wetresin mass)

In one embodiment the aqueous, alkaline solution comprising themelamine/urea/formaldehyde resin is present in about 38.0-93.0 parts ona solids mass basis and the multifunctional aromatic isocyanatecomponent is present in about 7.0-62.0 parts on a solids mass basis. Inone embodiment the aqueous, alkaline solution comprising themelamine/urea/formaldehyde resin is present in about 45.0-80.0 parts ona solids mass basis and the multifunctional aromatic isocyanatecomponent is present in about 20.0-55.0 parts on a solids mass basis. Inone embodiment the aqueous, alkaline solution comprising themelamine/urea/formaldehyde resin is present in about 50.0-65.0 parts ona solids mass basis and the multifunctional aromatic isocyanatecomponent is present in about 35.0-50.0 parts on a solids mass basis.

The adhesive emulsion can prepared by mixing the aqueous, alkalinemelamine/urea/formaldehyde resin with the multifunctional aromaticisocyanate component at the desired ratio of MUF resin tomultifunctional aromatic isocyanate component. This can be accomplishedby use of multi-component atomizers, such as those made by NorthernIndustrial Distributing Incorporated (Bemidji, Minn.), or proportionalmixing machines such as those made by The Willamette Valley Company(Eugene, Oreg.). Alternatively, the components could be mixed in thedesired ratio with a simple in-line static mix tube. In some cases themixture could be prepared in a small mix tank as long as the mixture wasutilized relatively quickly.

Upon initially mixing the adhesive exists as an emulsion in which thedispersed phase is dispersed within the continuous phase. This emulsionis surprisingly stable and low in viscosity for a period of time that issufficient for the adhesive emulsion to be applied to wooden elements inorder to form a wood-based composite. Although not wishing to be boundby any particular theory, it is hypothesized that as the emulsion ages,the isocyanate reacts with methylol groups on themelamine/urea/formaldehyde resin to form polyurethanes. Other reactions,including the reaction of the isocyanates with water to form polyureas,are also anticipated.

The pot-life of the adhesive emulsion depends on the mix ratio. Lowerlevels of isocyanate generally result in longer pot-life. The pot-lifeof the adhesive emulsion can be less than 15 minutes when the isocyanatecomponent is greater than about 50.0% on a solids mass basis, while thepot-life can be in excess of 60 minutes when the isocyanate is less thanabout 10.0% on a solids mass basis.

In another aspect, adhesive compositions are provided that include asuspended phase comprising a resin powder and a continuous phasecomprising a multifunctional aromatic isocyanate component. Thecomponents of these adhesive compositions are similar in nature to thoseof the adhesive emulsions provided herein. However, these adhesivecompositions have a suspended phase that is a resin powder.

The disclosed adhesive compositions are alternative formulationscompared to the adhesive emulsions but provide the same improvedcharacteristics when applied to the manufacture of wood-basedcomposites. These formulations can be used in place of the adhesiveemulsions. Mixing a powder into a liquid and then applying the adhesiveis different than mixing two liquids. Therefore, the adhesivecompositions provide an alternative mechanism for formulating anadhesive that eliminates the sometimes burdensome liquid-liquid mixingprocess required for the adhesive emulsions. For example, mixing thepowder into a resin before applying may be easier than using dualcomponent mix heads or in line static mixers to form adhesive emulsions.

In one embodiment, an adhesive composition is provided that includes;

-   -   (a) a suspended phase comprising melamine/urea/formaldehyde        resin powder; and    -   (b) a continuous phase comprising a multifunctional aromatic        isocyanate component;    -   wherein the melamine/urea/formaldehyde resin powder and the        multifunctional aromatic isocyanate component are present in a        ratio of about 1:99 to 55:45 on a solids mass basis.

In another embodiment, an adhesive composition is provided thatincludes;

-   -   (a) a suspended phase comprising a melamine/formaldehyde resin        powder; and    -   (b) a continuous phase comprising a multifunctional aromatic        isocyanate component;    -   wherein the melamine/formaldehyde resin powder and the        multifunctional aromatic isocyanate component are present in a        ratio of about 1:99 to 55:45 on a solids mass basis.

The adhesive compositions can be formed by simply mixing the MUF or MFresin powder into the continuous phase in the required proportions.

Wood-Based Composites

In another aspect, a wood-based composite is provided. In one embodimentthe wood-based composite includes wooden elements adhered together by apolyurethane polymer formed by the reaction of the continuous phase andthe dispersed phase of an adhesive emulsion according to the embodimentsdisclosed herein.

The wood-based composite can be formed using techniques and componentsknown to those of skill in the art.

In one embodiment, the wooden elements are selected from the groupconsisting of strands, flakes, particles, fibers, veneer, andcombinations thereof. As an example, these wooden elements can be cutfrom logs or subsections of logs based on aspen, poplar, fir, pine, oak,hemlock, maple, walnut, or elm.

In one embodiment, the wood-based composite is of a type selected fromthe group consisting of oriented strandboard, particleboard,medium-density fiberboard, oriented strand lumber, parallel strandlumber, laminated veneer lumber, laminated strand lumber, and plywood.

The Examples below disclosed the formation of OSB using the adhesiveemulsions according to the disclosed embodiments. In the Examples,two-part OSB is formed, with a core layer and a surface layer. Suchtwo-part OSB generally are known to those of skill in the art. In thedisclosed embodiments, the adhesive emulsion is applied to the surfacelayer of the OSB so as to facilitate removal of the OSB from the hotpress by reducing adhesion of the wood to the press platens.Accordingly, in one embodiment a wood-based composite is provided havingat least a core layer and a surface layer, wherein the surface layer istreated with the adhesive emulsion and the core layer is treated with anadhesive that is not the adhesive emulsion. In other embodiments awood-based composite is formed that is a single layer that is treatedwith the adhesive emulsion. In yet another embodiment, a multi-layerwood-based composite is provided in which two or more layers are treatedwith the adhesive emulsion.

In one embodiment, the wood-based composite further includes an additiveselected from the group consisting of a wax, a second adhesive, apreservative, a fire retardant, a coating, a sealant, a colorant, amarking, and combinations thereof.

In another aspect, a method of forming a wood-based composite isprovided. In one embodiment the method includes:

-   -   (a) coating a plurality of wooden elements with an adhesive        emulsion as disclosed herein to provide coated wooden elements;    -   (b) forming the coated wooden elements into a mat;    -   (c) applying pressure to the mat with a press; and    -   (d) heating the mat to form the wood-based composite.

Methods of forming wood-based composites are generally known to those ofskill in the art. In the present aspect, wood-based composites are madeby treating wooden elements with an adhesive emulsion according to thedisclosed embodiments. The adhesive-treated wooden elements are thenformed into a layered mat, which is then subjected to heat and pressure(usually in a hot-press) to form a composite, such as OSB,particleboard, medium density fiberboard, oriented strand lumber,parallel strand lumber, laminated veneer lumber or plywood. In thesecomposites additional additives such as waxes, other adhesives,preservatives, fire retardants, coatings, sealants, colorants, markingsor other can be incorporated into the composite.

In one embodiment the adhesive emulsion is applied at level of about1-15%, based on the dry mass of the wooden elements.

The step of forming the coated wooden elements into a mat may compriseforming two- or multi-layer mats that include wooden elements coatedwith different adhesives, wherein at least one layer comprises woodenelements coated with the adhesive emulsion.

The press typically used to form a wood-based composite provides bothpressure and heat (a “hot press”). The platens of the press are madefrom steel, which is known as a material to which prior art adhesives(e.g., pure PMDI) are known to adhere. When forming wood-basedcomposites according to the present method, the steps of applyingpressure and heating the mat to form the wood-based composite willexperience significantly less adhesion between the press platens and theformed wood-based composite due to the composition of the adhesiveemulsion and the resulting adhesive formed upon heating in the press.The Examples illustrate this effect in detail.

The following examples are intended to illustrate, not limit, thedisclosed embodiments.

EXAMPLES Example 1 Conventional Adhesive OSB

A conventional surface layer phenol/formaldehyde liquid adhesive, knownas 155C42, was manufactured by the Georgia-Pacific Resins Corporation(Atlanta, Ga.).

Oriented strand board (OSB) that was representative of conventional OSBwas produced on a laboratory-scale in the following manner. Woodenstrands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″ long, aspen andpoplar species) designated as “core-layer strands” were dried to amoisture content of about 2.5-3.5% and were then transferred into afront-load, cylindrical-shaped “blender” compartment (2′ depth, 6′diameter). The axis of rotation of the blender was parallel to thelaboratory floor. The rotating interior surface of the blendercompartment was equipped with pegs (2″ height, 0.25″ diameter). Therotation rate of the blender was set at 11 rpm, which was appropriate tocause the strands to be carried to the top of the interior region of theblender compartment and to then fall to the bottom of the compartment ina cascading, “waterfall-like” action. The blender was further equippedwith a spray application system for molten neat wax as well as a sprayapplication system for liquid bonding resins. A slack wax, known as 431B(manufactured by the International Group Incorporated in Toronto,Ontario, Canada), was heated to a temperature of 225° F. and thensprayed onto the wooden strands at a loading level of 0.5% based on thedry mass of the wood. An isocyanate-based bonding resin, known asLupranate M20FB (manufactured by the BASF Corporation in Wyandotte,Mich.), was then sprayed onto the strands at a loading level of 4.0%based on the dry mass of the wood. The treated core-layer strands werethen removed from the blender.

Additional wooden strands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″long, aspen and poplar species) designated as “core-layer strands” weredried to a moisture content of about 1.5-2.5% and were then loaded intothe blender compartment. A slack wax, known as 431B ((manufactured bythe International Group Incorporated in Toronto, Ontario, Canada), washeated to a temperature of 225° F. and then sprayed onto the woodenstrands at a loading level of 0.5% based on the dry mass of the wood. Aphenol-formaldehyde based bonding resin, known as 155C42 (manufacturedby the Georgia Pacific Resins Corporation in Decatur, Ga.), was thensprayed onto the strands at a loading level of 2.0% based on the solidscontent of the resin and the dry mass of the wood. The treatedcore-layer strands were then removed from the blender.

The treated strands were formed on top of a screen and caul plate into afour-layered mat that was comprised of one bottom surface layer, twomiddle core layers, and one top surface layer. The length of the mat was24″ and the width of the mat was also 24″. The strands in the surfacelayers were oriented in a direction that was generally parallel to onemajor axis of the mat, while the strands in the core layer were orientedin a direction that was generally parallel to the other major axis ofthe mat. The mass of each of the four layers was about 1070-1085 g. Thethickness of the mat was about 5″.

The mat, as well as the caul plate and screen that were supporting themat, were then transferred onto the bottom platen of an open hot-press.The top and bottom platens were maintained at a surface temperature of420° F. A control system was immediately activated in order to beginclosing the gap between the top and bottom platens until the distancebetween them was 0.719″. The time required to achieve this compressionprocess was about 60 s. The maximum pressure exerted on the mat wasabout 500-650 psi. The gap between the platens was maintained at 0.719″for a period of 190 s and was then increased to 0.749″ over a period of30 s. The gap between the platens was then rapidly opened and theresulting, consolidated OSB panel was removed from the press.

The hot OSB panel was then transferred into an oven, which wasmaintained at a temperature of 80° C. for a period of 24 h. The panelwas then removed from the oven and placed into a conditioning chamberthat was maintained at a relative humidity of 50% and a temperature of20° C.

Three replicate panels were made in this manner. One test specimen(8″×16″) was cut from each conditioned laboratory panel. Each testspecimen was weighed and measured for thickness at five marked locationsalong the center of the specimen. Each test specimen was then submergedunder 1″ of water (T=20° C.) for a period of 48 hours. Each testspecimen was then removed from the water and measured for mass andthickness at each of the previously measured locations along the centerof the specimen. Each test specimen was then transferred into an ovenand dried at a temperature of 80° C. for a period of 48 hours. The driedspecimens were also measured for mass and thickness at each of thepreviously measured locations along the center of the specimen. Based onthese measurements calculations were made regarding the moisture contentand the thickness swell that occurred during the water-soak procedure.The results are presented in Table 1. In general:

Moisture Content=100%(water mass in the specimen)/(dry mass of thespecimen)

Wet Thickness Swell=100%(thickness after soaking for two days−initialthickness)/(initial thickness)

Redry Thickness Swell=100%(thickness after redry−initialthickness)/(initial thickness)

TABLE 1 Test values for OSB made with PF resin in the surface layerMOISTURE THICKNESS SWELL (%) CONTENT (%) AFTER SOAKING FOR AFTER SOAKINGTWO DAYS & THEN SAMPLE FOR TWO DAYS DRYING FOR TWO DAYS 1 34.6 14.6 233.1 13.8 3 32.5 15.0 AVERAGE 33.4 14.5

Example 2 Conventional Premium Adhesive OSB

Oriented strand board (OSB) that was representative of conventional,premium OSB was produced on a laboratory-scale in the following manner.Wooden strands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″ long, aspenand poplar species) designated as “core-layer strands” were dried to amoisture content of about 2.5-3.5% and were then transferred into afront-load, cylindrical-shaped “blender” compartment (2′ depth, 6′diameter). The axis of rotation of the blender was parallel to thelaboratory floor. The rotating interior surface of the blendercompartment was equipped with pegs (2″ height, 0.25″ diameter). Therotation rate of the blender was set at 11 rpm, which was appropriate tocause the strands to be carried to the top of the interior region of theblender compartment and to then fall to the bottom of the compartment ina cascading, “waterfall-like” action. The blender was further equippedwith a spray application system for molten neat wax as well as a sprayapplication system for liquid bonding resins. A slack wax, known as 431B((manufactured by the International Group Incorporated in Toronto,Ontario, Canada), was heated to a temperature of 225° F. and thensprayed onto the wooden strands at a loading level of 0.5% based on thedry mass of the wood. An isocyanate-based bonding resin, known asLupranate M20FB (manufactured by the BASF Corporation in Wyandotte,Mich.), was then sprayed onto the strands at a loading level of 4.0%based on the dry mass of the wood. The treated core-layer strands werethen removed from the blender.

Additional wooden strands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″long, aspen and poplar species) designated as “core-layer strands” weredried to a moisture content of about 1.5-2.5% and were then loaded intothe blender compartment. A slack wax, known as 431B (manufactured by theInternational Group Incorporated in Toronto, Ontario, Canada), washeated to a temperature of 225° F. and then sprayed onto the woodenstrands at a loading level of 0.5% based on the dry mass of the wood. Anisocyanate-based bonding resin, known as Lupranate M20FB (manufacturedby the BASF Corporation in Wyandotte, Mich.), was then sprayed onto thestrands at a loading level of 2.0% based on the solids content of theresin and the dry mass of the wood. The treated core-layer strands werethen removed from the blender.

The treated strands were formed on top of a screen and caul plate into afour-layered mat that was comprised of one bottom surface layer, twomiddle core layers, and one top surface layer. The length of the mat was24″ and the width of the mat was also 24″. The strands in the surfacelayers were oriented in a direction that was generally parallel to oneof the major axis of the mat, while the strands in the core layer wereoriented in a direction that was generally parallel to the other majoraxis of the mat. The mass of each of the four layers was about 1070-1085g. The thickness of the mat was about 5″.

The mat, as well as the caul plate and screen that were supporting themat, were then transferred onto the bottom platen of an open hot-press.The top and bottom platens were maintained at a surface temperature of420° F. A control system was immediately activated in order to beginclosing the gap between the top and bottom platens until the distancebetween them was 0.719″. The time required to achieve this compressionprocess was about 60 s. The maximum pressure exerted on the mat wasabout 500-650 psi. The gap between the platens was maintained at 0.719″for a period of 190 s and was then increased to 0.749″ over a period of30 s. The gap between the platens was then rapidly opened and theresulting, consolidated OSB panel was removed from the press.

The hot OSB panel was then transferred into an oven, which wasmaintained at a temperature of 80° C. for a period of 24 h. The panelwas then removed from the oven and placed into a conditioning chamberthat was maintained at a relative humidity of 50% and a temperature of20° C.

Three replicate panels were made in this manner. One test specimen(8″×16″) was cut from each conditioned laboratory panel. Each testspecimen was weighed and measured for thickness at five marked locationsalong the center of the specimen. Each test specimen was then submergedunder 1″ of water (T=20° C.) for a period of 48 hours. Each testspecimen was then removed from the water and measured for mass andthickness at each of the previously measured locations along the centerof the specimen. Each test specimen was then transferred into an ovenand dried at a temperature of 80° C. for a period of 48 hours. The driedspecimens were also measured for mass and thickness at each of thepreviously measured locations along the center of the specimen. Based onthese measurements calculations were made regarding the moisture contentand the thickness swell that occurred during the water-soak procedure.The results are presented in Table 2. In general:

Moisture Content=100%(water mass in the specimen)/(dry mass of thespecimen)

Wet Thickness Swell=100%(thickness after soaking for two days−initialthickness)/(initial thickness)

Swell=100%(thickness after redry−initial thickness)/(initial thickness)

TABLE 2 Test values for OSB made with PMDI only in the surface layerMOISTURE THICKNESS SWELL (%) CONTENT (%) AFTER SOAKING FOR AFTER SOAKINGTWO DAYS & THEN SAMPLE FOR TWO DAYS DRYING FOR TWO DAYS 1 14.7 6.1 216.8 5.1 3 16.7 7.2 AVERAGE 16.1 6.1

Example 3 MUF Adhesive OSB

Oriented strand board (OSB) that was representative of non-conventional,OSB was produced on a laboratory-scale in the following manner. Woodenstrands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″ long, aspen andpoplar species) designated as “core-layer strands” were dried to amoisture content of about 2.5-3.5% and were then transferred into afront-load, cylindrical-shaped “blender” compartment (2′ depth, 6′diameter). The axis of rotation of the blender was parallel to thelaboratory floor. The rotating interior surface of the blendercompartment was equipped with pegs (2″ height, 0.25″ diameter). Therotation rate of the blender was set at 11 rpm, which was appropriate tocause the strands to be carried to the top of the interior region of theblender compartment and to then fall to the bottom of the compartment ina cascading, “waterfall-like” action. The blender was further equippedwith a spray application system for molten neat wax as well as a sprayapplication system for liquid bonding resins. A slack wax, known as 431B((manufactured by the International Group Incorporated in Toronto,Ontario, Canada), was heated to a temperature of 225° F. and thensprayed onto the wooden strands at a loading level of 0.5% based on thedry mass of the wood. An isocyanate-based bonding resin, known asLupranate M20FB (manufactured by the BASF Corporation in Wyandotte,Mich.), was then sprayed onto the strands at a loading level of 4.0%based on the dry mass of the wood. The treated core-layer strands werethen removed from the blender.

Additional wooden strands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″long, aspen and poplar species) designated as “core-layer strands” weredried to a moisture content of about 1.5-2.5% and were then loaded intothe blender compartment. A slack wax, known as 431B ((manufactured bythe International Group Incorporated in Toronto, Ontario, Canada), washeated to a temperature of 225° F. and then sprayed onto the woodenstrands at a loading level of 0.5% based on the dry mass of the wood. Amelamine/urea/formaldehyde bonding resin, known as 401W67 (pH=8.15)(manufactured by the Georgia-Pacific Resins Corporation in Atlanta,Ga.), was then sprayed onto the strands at a loading level of 2.0% basedon the solids content of the resin and the dry mass of the wood. Thetreated core-layer strands were then removed from the blender.

The treated strands were formed on top of a screen and caul plate into afour-layered mat that was comprised of one bottom surface layer, twomiddle core layers, and one top surface layer. The length of the mat was24″ and the width of the mat was also 24″. The strands in the surfacelayers were oriented in a direction that was generally parallel to oneof the major axis of the mat, while the strands in the core layer wereoriented in a direction that was generally parallel to the other majoraxis of the mat. The mass of each of the four layers was about 1070-1085g. The thickness of the mat was about 5″.

The mat, as well as the caul plate and screen that were supporting themat, were then transferred onto the bottom platen of an open hot-press.The top and bottom platens were maintained at a surface temperature of420° F. A control system was immediately activated in order to beginclosing the gap between the top and bottom platens until the distancebetween them was 0.719″. The time required to achieve this compressionprocess was about 60 s. The maximum pressure exerted on the mat wasabout 500-650 psi. The gap between the platens was maintained at 0.719″for a period of 190 s and was then increased to 0.749″ over a period of30 s. The gap between the platens was then rapidly opened and theresulting, consolidated OSB panel was removed from the press.

The hot OSB panel was then transferred into an oven, which wasmaintained at a temperature of 80° C. for a period of 24 h. The panelwas then removed from the oven and placed into a conditioning chamberthat was maintained at a relative humidity of 50% and a temperature of20° C.

Three replicate panels were made in this manner. One test specimen(8″×16″) was cut from each conditioned laboratory panel. Each testspecimen was weighed and measured for thickness at five marked locationsalong the center of the specimen. Each test specimen was then submergedunder 1″ of water (T=20° C.) for a period of 48 hours. Each testspecimen was then removed from the water and measured for mass andthickness at each of the previously measured locations along the centerof the specimen. Each test specimen was then transferred into an ovenand dried at a temperature of 80° C. for a period of 48 hours. The driedspecimens were also measured for mass and thickness at each of thepreviously measured locations along the center of the specimen. Based onthese measurements calculations were made regarding the moisture contentand the thickness swell that occurred during the water-soak procedure.The results are presented in Table 3. In general:

Moisture Content=100%(water mass in the specimen)/(dry mass of thespecimen)

Wet Thickness Swell=100%(thickness after soaking for two days−initialthickness)/(initial thickness)

Redry Thickness Swell=100%(thickness after redry−initialthickness)/(initial thickness)

TABLE 3 Test values for OSB made with MUF in the surface layer MOISTURETHICKNESS SWELL (%) CONTENT (%) AFTER SOAKING FOR AFTER SOAKING TWO DAYS& THEN SAMPLE FOR TWO DAYS DRYING FOR TWO DAYS 1 29.6 15.9 2 26.8 14.0 326.1 14.2 AVERAGE 27.5 14.7

Example 4 Exemplary OSB Formed with Adhesive Emulsion

Oriented strand board (OSB) that was representative of non-conventional,OSB was produced on a laboratory-scale in the following manner. Woodenstrands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″ long, aspen andpoplar species) designated as “core-layer strands” were dried to amoisture content of about 2.5-3.5% and were then transferred into afront-load, cylindrical-shaped “blender” compartment (2′ depth, 6′diameter). The axis of rotation of the blender was parallel to thelaboratory floor. The rotating interior surface of the blendercompartment was equipped with pegs (2″ height, 0.25″ diameter). Therotation rate of the blender was set at 11 rpm, which was appropriate tocause the strands to be carried to the top of the interior region of theblender compartment and to then fall to the bottom of the compartment ina cascading, “waterfall-like” action. The blender was further equippedwith a spray application system for molten neat wax as well as a sprayapplication system for liquid bonding resins. A slack wax, known as 431B(manufactured by the International Group Incorporated in Toronto,Ontario, Canada), was heated to a temperature of 225° F. and thensprayed onto the wooden strands at a loading level of 0.5% based on thedry mass of the wood. An isocyanate-based bonding resin, known asLupranate M20FB (manufactured by the BASF Corporation in Wyandotte,Mich.), was then sprayed onto the strands at a loading level of 4.0%based on the dry mass of the wood. The treated core-layer strands werethen removed from the blender.

Additional wooden strands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″long, aspen and poplar species) designated as “core-layer strands” weredried to a moisture content of about 1.5-2.5% and were then loaded intothe blender compartment. A slack wax, known as 431B (manufactured by theInternational Group Incorporated in Toronto, Ontario, Canada), washeated to a temperature of 225° F. and then sprayed onto the woodenstrands at a loading level of 0.5% based on the dry mass of the wood. Amelamine/urea/formaldehyde bonding resin, known as 401W67 (pH=8.15)(manufactured by the Georgia-Pacific Resins Corporation in Atlanta,Ga.), was mixed with PMDI (Lupranate M20FB) at a ratio of 90.0:10.0 on awet mass basis. On a solids basis this ratio was MUF (86.1 parts bymass) to PMDI (13.9 parts by mass). This mixture existed as a lowviscosity emulsion, which was sprayed onto the strands at a loadinglevel of 2.0% based on the solids content of the resin and the dry massof the wood. The application of the mixed adhesive formulation wascompleted within about 20 minutes of preparation. The treated core-layerstrands were then removed from the blender.

The treated strands were formed on top of a screen and caul plate into afour-layered mat that was comprised of one bottom surface layer, twomiddle core layers, and one top surface layer. The length of the mat was24″ and the width of the mat was also 24″. The strands in the surfacelayers were oriented in a direction that was generally parallel to oneof the major axis of the mat, while the strands in the Theseformulations can be used in place of the emulsions. Mixing a powder intoa liquid and then applying the adhesive is different than mixing twoliquids. Someone could try to use this method to get around the patentor just decide that mixing the powder into the resin before applying iseasier than using dual component mix heads or in line static mixerslayer were oriented in a direction that was generally parallel to theother major axis of the mat. The mass of each of the four layers wasabout 1070-1085 g. The thickness of the mat was about 5″.

The mat, as well as the caul plate and screen that were supporting themat, were then transferred onto the bottom platen of an open hot-press.The top and bottom platens were maintained at a surface temperature of420° F. A control system was immediately activated in order to beginclosing the gap between the top and bottom platens until the distancebetween them was 0.719″. The time required to achieve this compressionprocess was about 60 s. The maximum pressure exerted on the mat wasabout 500-650 psi. The gap between the platens was maintained at 0.719″for a period of 190 s and was then increased to 0.749″ over a period of30 s. The gap between the platens was then rapidly opened and theresulting, consolidated OSB panel was removed from the press.

The hot OSB panel was then transferred into an oven, which wasmaintained at a temperature of 80° C. for a period of 24 h. The panelwas then removed from the oven and placed into a conditioning chamberthat was maintained at a relative humidity of 50% and a temperature of20° C.

Three replicate panels were made in this manner. One test specimen(8″×16″) was cut from each conditioned laboratory panel. Each testspecimen was weighed and measured for thickness at five marked locationsalong the center of the specimen. Each test specimen was then submergedunder 1″ of water (T=20° C.) for a period of 48 hours. Each testspecimen was then removed from the water and measured for mass andthickness at each of the previously measured locations along the centerof the specimen. Each test specimen was then transferred into an ovenand dried at a temperature of 80° C. for a period of 48 hours. The driedspecimens were also measured for mass and thickness at each of thepreviously measured locations along the center of the specimen. Based onthese measurements calculations were made regarding the moisture contentand the thickness swell that occurred during the water-soak procedure.The results are presented in Table 4. In general:

Moisture Content=100%(water mass in the specimen)/(dry mass of thespecimen)

Wet Thickness Swell=100%(thickness after soaking for two days−initialthickness)/(initial thickness)

Redry Thickness Swell=100%(thickness after redry−initialthickness)/(initial thickness)

TABLE 4 Test values for OSB made with a MUF (86.1 parts by dry mass) &PMDI (13.9 parts by mass) mixed adhesive composition in the surfacelayer MOISTURE THICKNESS SWELL (%) CONTENT (%) AFTER SOAKING FOR AFTERSOAKING TWO DAYS & THEN SAMPLE FOR TWO DAYS DRYING FOR TWO DAYS 1 24.512.1 2 24.5 11.7 3 33.1 14.0 AVERAGE 27.4 12.6

Example 5 Exemplary OSB Formed with Adhesive Emulsion

Oriented strand board (OSB) that was representative of non-conventional,OSB was produced on a laboratory-scale in the following manner. Woodenstrands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″ long, aspen andpoplar species) designated as “core-layer strands” were dried to amoisture content of about 2.5-3.5% and were then transferred into afront-load, cylindrical-shaped “blender” compartment (2′ depth, 6′diameter). The axis of rotation of the blender was parallel to thelaboratory floor. The rotating interior surface of the blendercompartment was equipped with pegs (2″ height, 0.25″ diameter). Therotation rate of the blender was set at 11 rpm, which was appropriate tocause the strands to be carried to the top of the interior region of theblender compartment and to then fall to the bottom of the compartment ina cascading, “waterfall-like” action. The blender was further equippedwith a spray application system for molten neat wax as well as a sprayapplication system for liquid bonding resins. A slack wax, known as 431B(manufactured by the International Group Incorporated in Toronto,Ontario, Canada), was heated to a temperature of 225° F. and thensprayed onto the wooden strands at a loading level of 0.5% based on thedry mass of the wood. An isocyanate-based bonding resin, known asLupranate M20FB (manufactured by the BASF Corporation in Wyandotte,Mich.), was then sprayed onto the strands at a loading level of 4.0%based on the dry mass of the wood. The treated core-layer strands werethen removed from the blender.

Additional wooden strands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″long, aspen and poplar species) designated as “core-layer strands” weredried to a moisture content of about 1.5-2.5% and were then loaded intothe blender compartment. A slack wax, known as 431B (manufactured by theInternational Group Incorporated in Toronto, Ontario, Canada), washeated to a temperature of 225° F. and then sprayed onto the woodenstrands at a loading level of 0.5% based on the dry mass of the wood. Amelamine/urea/formaldehyde bonding resin, known as 401W67 (pH=8.15)(manufactured by the Georgia-Pacific Resins Corporation in Atlanta,Ga.), was mixed with PMDI (Lupranate M20FB) at a ratio of 80.0:20.0 on awet mass basis. On a solids basis this ratio was MUF (72.2 parts bymass) to PMDI (27.8 parts by mass). This mixture existed as a lowviscosity emulsion, which was sprayed onto the strands at a loadinglevel of 2.0% based on the solids content of the resin and the dry massof the wood. The application of the mixed adhesive formulation wascompleted within about 20 minutes of preparation. The treated core-layerstrands were then removed from the blender.

The treated strands were formed on top of a screen and caul plate into afour-layered mat that was comprised of one bottom surface layer, twomiddle core layers, and one top surface layer. The length of the mat was24″ and the width of the mat was also 24″. The strands in the surfacelayers were oriented in a direction that was generally parallel to oneof the major axis of the mat, while the strands in the core layer wereoriented in a direction that was generally parallel to the other majoraxis of the mat. The mass of each of the four layers was about 1070-1085g. The thickness of the mat was about 5″.

The mat, as well as the caul plate and screen that were supporting themat, were then transferred onto the bottom platen of an open hot-press.The top and bottom platens were maintained at a surface temperature of420° F. A control system was immediately activated in order to beginclosing the gap between the top and bottom platens until the distancebetween them was 0.719″. The time required to achieve this compressionprocess was about 60 s. The maximum pressure exerted on the mat wasabout 500-650 psi. The gap between the platens was maintained at 0.719″for a period of 190 s and was then increased to 0.749″ over a period of30 s. The gap between the platens was then rapidly opened and theresulting, consolidated OSB panel was removed from the press.

The hot OSB panel was then transferred into an oven, which wasmaintained at a temperature of 80° C. for a period of 24 h. The panelwas then removed from the oven and placed into a conditioning chamberthat was maintained at a relative humidity of 50% and a temperature of20° C.

Three replicate panels were made in this manner. One test specimen(8″×16″) was cut from each conditioned laboratory panel. Each testspecimen was weighed and measured for thickness at five marked locationsalong the center of the specimen. Each test specimen was then submergedunder 1″ of water (T=20° C.) for a period of 48 hours. Each testspecimen was then removed from the water and measured for mass andthickness at each of the previously measured locations along the centerof the specimen. Each test specimen was then transferred into an ovenand dried at a temperature of 80° C. for a period of 48 hours. The driedspecimens were also measured for mass and thickness at each of thepreviously measured locations along the center of the specimen. Based onthese measurements calculations were made regarding the moisture contentand the thickness swell that occurred during the water-soak procedure.The results are presented in Table 5. In general:

Moisture Content=100%(water mass in the specimen)/(dry mass of thespecimen)

Wet Thickness Swell=100%(thickness after soaking for two days−initialthickness)/(initial thickness)

Redry Thickness Swell=100%(thickness after redry−initialthickness)/(initial thickness)

TABLE 5 Test values for OSB made with a MUF (72.2 parts by dry mass) &PMDI (27.8 parts by mass) mixed adhesive composition in the surfacelayer MOISTURE THICKNESS SWELL (%) CONTENT (%) AFTER SOAKING FOR AFTERSOAKING TWO DAYS & THEN SAMPLE FOR TWO DAYS DRYING FOR TWO DAYS 1 25.010.8 2 24.3 11.1 3 23.1 14.5 AVERAGE 24.1 12.1

Example 6 Exemplary OSB Formed with Adhesive Emulsion

Oriented strand board (OSB) that was representative of non-conventional,OSB was produced on a laboratory-scale in the following manner. Woodenstrands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″ long, aspen andpoplar species) designated as “core-layer strands” were dried to amoisture content of about 2.5-3.5% and were then transferred into afront-load, cylindrical-shaped “blender” compartment (2′ depth, 6′diameter). The axis of rotation of the blender was parallel to thelaboratory floor. The rotating interior surface of the blendercompartment was equipped with pegs (2″ height, 0.25″ diameter). Therotation rate of the blender was set at 11 rpm, which was appropriate tocause the strands to be carried to the top of the interior region of theblender compartment and to then fall to the bottom of the compartment ina cascading, “waterfall-like” action. The blender was further equippedwith a spray application system for molten neat wax as well as a sprayapplication system for liquid bonding resins. A slack wax, known as 431B(manufactured by the International Group Incorporated in Toronto,Ontario, Canada), was heated to a temperature of 225° F. and thensprayed onto the wooden strands at a loading level of 0.5% based on thedry mass of the wood. An isocyanate-based bonding resin, known asLupranate M20FB (manufactured by the BASF Corporation in Wyandotte,Mich.), was then sprayed onto the strands at a loading level of 4.0%based on the dry mass of the wood. The treated core-layer strands werethen removed from the blender.

Additional wooden strands (25-45 mils thick, 0.25-1.5″ wide, 0.25-5.0″long, aspen and poplar species) designated as “core-layer strands” weredried to a moisture content of about 1.5-2.5% and were then loaded intothe blender compartment. A slack wax, known as 431B (manufactured by theInternational Group Incorporated in Toronto, Ontario, Canada), washeated to a temperature of 225° F. and then sprayed onto the woodenstrands at a loading level of 0.5% based on the dry mass of the wood. Amelamine/urea/formaldehyde bonding resin, known as 401W67 (pH=8.15)(manufactured by the Georgia-Pacific Resins Corporation in Atlanta,Ga.), was mixed with PMDI (Lupranate M20FB) at a ratio of 70.0:30.0 on awet mass basis. On a solids basis this ratio was MUF (58.3 parts bymass) to PMDI (41.7 parts by mass). This mixture existed as a lowviscosity emulsion, which was sprayed onto the strands at a loadinglevel of 2.0% based on the solids content of the resin and the dry massof the wood. The application of the mixed adhesive formulation wascompleted within about 20 minutes of preparation. The treated core-layerstrands were then removed from the blender.

The treated strands were formed on top of a screen and caul plate into afour-layered mat that was comprised of one bottom surface layer, twomiddle core layers, and one top surface layer. The length of the mat was24″ and the width of the mat was also 24″. The strands in the surfacelayers were oriented in a direction that was generally parallel to oneof the major axis of the mat, while the strands in the core layer wereoriented in a direction that was generally parallel to the other majoraxis of the mat. The mass of each of the four layers was about 1070-1085g. The thickness of the mat was about 5″.

The mat, as well as the caul plate and screen that were supporting themat, were then transferred onto the bottom platen of an open hot-press.The top and bottom platens were maintained at a surface temperature of420° F. A control system was immediately activated in order to beginclosing the gap between the top and bottom platens until the distancebetween them was 0.719″. The time required to achieve this compressionprocess was about 60 s. The maximum pressure exerted on the mat wasabout 500-650 psi. The gap between the platens was maintained at 0.719″for a period of 190 s and was then increased to 0.749″ over a period of30 s. The gap between the platens was then rapidly opened and theresulting, consolidated OSB panel was removed from the press.

The hot OSB panel was then transferred into an oven, which wasmaintained at a temperature of 80° C. for a period of 24 h. The panelwas then removed from the oven and placed into a conditioning chamberthat was maintained at a relative humidity of 50% and a temperature of20° C.

Three replicate panels were made in this manner. One test specimen(8″×16″) was cut from each conditioned laboratory panel. Each testspecimen was weighed and measured for thickness at five marked locationsalong the center of the specimen. Each test specimen was then submergedunder 1″ of water (T=20° C.) for a period of 48 hours. Each testspecimen was then removed from the water and measured for mass andthickness at each of the previously measured locations along the centerof the specimen. Each test specimen was then transferred into an ovenand dried at a temperature of 80° C. for a period of 48 hours. The driedspecimens were also measured for mass and thickness at each of thepreviously measured locations along the center of the specimen. Based onthese measurements calculations were made regarding the moisture contentand the thickness swell that occurred during the water-soak procedure.The results are presented in Table 6. In general:

Moisture Content=100%(water mass in the specimen)/(dry mass of thespecimen)

Wet Thickness Swell=100%(thickness after soaking for two days−initialthickness)/(initial thickness)

Redry Thickness Swell=100%(thickness after redry−initialthickness)/(initial thickness)

TABLE 6 Test values for OSB made with a MUF (58.3 parts by dry mass) &PMDI (41.7 parts by mass) mixed adhesive composition in the surfacelayer MOISTURE THICKNESS SWELL (%) CONTENT (%) AFTER SOAKING FOR AFTERSOAKING TWO DAYS & THEN SAMPLE FOR TWO DAYS DRYING FOR TWO DAYS 1 21.68.9 2 22.7 10.2 3 20.9 8.0 AVERAGE 21.8 9.0

Example 7 Characterization of Conventional and Exemplary OSB

Laboratory OSB sections (16″×8″) described in Examples 1-6 were allsubmerged under 1″ of water (20° C.) for a period of 4 hours. All of thespecimens were removed from the water, placed adjacent to each other,and then inspected. The OSB described in Example 1 (with a PF resin inthe surface layer) had a relatively dark surface appearance, while theother OSB types described in examples 2-6 had a relatively light surfaceappearance. The results are summarized in Table 7.

TABLE 7 Summary of test data from Examples 1-6 samples MOISTURETHICKNESS SWELL (%) CONTENT (%) AFTER SOAKING FOR SURFACE AFTER SOAKINGTWO DAYS & THEN WET OSB EXAMPLE RESIN TYPE FOR TWO DAYS DRYING FOR TWODAYS APPEARANCE 1 PF 33.4 14.5 DARK 2 PMDI 16.1 6.1 LIGHT 3 MUF 27.514.7 LIGHT 4 MUF (86.1)/ 27.4 12.6 LIGHT PMDI (13.9) 5 MUF (72.2)/ 24.112.1 LIGHT PMDI (27.8) 6 MUF (58.3)/ 21.8 9.0 LIGHT PMDI (41.7)

Example 8 Press Platen Adhesion

One desirable benefit of the disclosed compositions is the reduction ofadhesion to press platens during formation of a wood product (e.g.,OSB). Representative adhesive emulsions of the present disclosure, whichcontain both MUF and PMDI in the exemplary embodiments, were shown toexhibit reduced adhesion compared to OSB formed using only PMDI.

A lap shear bond testing apparatus was used to measure the bond strengthof southern yellow pine strands bonded to an A-36 carbon steel coupon.Adhesive was applied to a wood strand that was previously cut fromveneer. The adhesive compositions included 100% PMDI; 100% MUF; 100% PF;and blends of PMDI/MUF according to the present disclosure. The sampleswere prepared in accordance with the previous examples.

The strand was placed into the heated platen testing apparatus alongwith an A-36 carbon steel coupon, a common material used for heatedpress platens used to form wood products (e.g., OSB). The bond area was25 mm by 20 mm (500 mm₂). The apparatus pressed the wood strand andsteel coupon together with a force of 60 psi and the press heads heatedto 213° C. Pressure and heat were applied for 30 seconds. The pressheads were then pulled away from the bonding area. The bond was thenbroken by pulling the wooden strand and steel coupon in oppositedirections. A load cell measured the force required to break each bond.20 bonds for each adhesive were tested.

The results of the lap shear test are illustrated in the FIGURE. Astatistical software package was used to determine the difference in lapshear bond strength at a 95% confidence interval level (“95% CI for theMean”). Groups with non-overlapping interval bars are significantlydifferent at a 95% confidence level. PMDI showed the most force requiredto separate, which indicates the most adhesion (“sticking”) to thecoupon. This is unsurprising, as PMDI is known to adhere to pressplatens when forming wood products, a problem the present disclosure ismeant to address. PMDI/MUF blends, exemplary of the disclosedembodiments, demonstrated reduced adhesion.

While illustrative embodiments have been illustrated and described, itwill be appreciated that various changes can be made therein withoutdeparting from the spirit and scope of the invention.

I/We claim:
 1. A wood-based composite comprising wooden elements adheredtogether by a polyurethane polymer formed by the reaction of acontinuous phase and a dispersed phase of an adhesive emulsion,comprising: (a) a continuous phase, comprising an aqueous, alkalinesolution comprising a melamine/urea/formaldehyde resin; and (b) adispersed phase, comprising a multifunctional aromatic isocyanatecomponent; wherein the aqueous, alkaline solution comprising themelamine/urea/formaldehyde resin has a percent solids content of about1.0% to about 90.0%; and wherein the melamine/urea/formaldehyde resinand the multifunctional aromatic isocyanate component are present in aratio of about 92:8 to about 40:60 on a solids mass basis.
 2. Thewood-based composite of claim 1, wherein the wooden elements areselected from the group consisting of strands, flakes, particles,fibers, veneer, and combinations thereof.
 3. The wood-based composite ofclaim 1, wherein the wood-based composite is of a type selected from thegroup consisting of oriented strandboard, particleboard, medium-densityfiberboard, oriented strand lumber, parallel strand lumber, laminatedveneer lumber, laminated strand lumber, and plywood.
 4. The wood-basedcomposite of claim 1, further comprising an additive selected from thegroup consisting of a wax, a second adhesive, a preservative, a fireretardant, a coating, a sealant, a colorant, a marking, and combinationsthereof.
 5. A method of forming a wood-based composite, comprising: (a)coating a plurality of wooden elements with an adhesive emulsion toprovide coated wooden elements, the adhesive emulsion comprising: (i) acontinuous phase, comprising an aqueous, alkaline solution comprising amelamine/urea/formaldehyde resin; and (ii) a dispersed phase, comprisinga multifunctional aromatic isocyanate component; wherein the aqueous,alkaline solution comprising the melamine/urea/formaldehyde resin has apercent solids content of about 1.0% to about 90.0%; and wherein themelamine/urea/formaldehyde resin and the multifunctional aromaticisocyanate component are present in a ratio of about 92:8 to about 40:60on a solids mass basis; (b) forming the coated wooden elements into amat; (c) applying pressure to the mat with a press; and (d) heating themat to form the wood-based composite.
 6. The method of claim 5, whereinthe adhesive emulsion is applied at level of about 1-15%, based on thedry mass of the wooden elements.
 7. An adhesive composition, comprising;(a) a suspended phase comprising melamine/urea/formaldehyde resinpowder; and (b) a continuous phase comprising a multifunctional aromaticisocyanate component; wherein the melamine/urea/formaldehyde resinpowder and the multifunctional aromatic isocyanate component are presentin a ratio of about 1:99 to 55:45 on a solids mass basis.
 8. An adhesivecomposition, comprising; (a) a suspended phase comprising amelamine/formaldehyde resin powder; and (b) a continuous phasecomprising a multifunctional aromatic isocyanate component; wherein themelamine/formaldehyde resin powder and the multifunctional aromaticisocyanate component are present in a ratio of about 1:99 to 55:45 on asolids mass basis.